外子

例句：

1. 1. He is the only son of a wealthy family.
   他是富裕家庭的唯一儿子。
2. 2. She has been married for over ten years.
   她结婚十年了。
3. 3. They have two children, one boy and one girl.
   他们有两个孩子，一个男孩和一个女孩。